They always take liberties with the storylines in DC movies. I can't think of one DC movie where they haven't. Don't write it off just yet... Besides, I'm not seeing a downside to Michelle Borth playing Mary Marvel

Bill Potts wasn't as bad as the new lot but that's about as far as I'm prepared to go. It's difficult to draw comparisons to the older characters because the acting style - and feel of the show - has changed completely. Adric will always be at the bottom and deservedly so. Mel and Ace did what they were meant to do... play off the Doctor in that hammy, overly theatrical style we'd become accustomed to.
Going back to the new bunch, I think Yaz or Graham would work on their own, they just don't work as a group. I would be more inclined to watch the show if it was the Doctor and one companion.